1. Field of the Invention
The present invention relates to a developer holding apparatus that incorporates a toner level detecting mechanism, the toner detecting mechanism detecting a remaining amount of toner in the developer holding apparatus. The present invention also relates to a developing unit that incorporates the developer holding apparatus and an image forming apparatus that incorporates the developing holding apparatus.
2. Description of the Related Art
One type of toner level detector is disclosed in, for example, Japanese patent publication No. 2006-23537. The toner level detector is disposed in a toner reservoir in a developing unit, and employs a toner agitator that rotates to agitate the toner. The amount of toner remaining in the toner reservoir is detected based on the rotation of the toner agitator. The agitator has a crank portion that agitates the toner. The agitator is rotated by a drive shaft until the crank portion reaches its top dead center TDC. The crank portion then falls by gravity to land on the pile of the toner.
The aforementioned toner detector detects the toner level based on various items of information when the crank portion of the agitator falls by gravity to land on the pile of the toner. Therefore, it is important for the agitator to accurately land on the surface of the toner without sinking into the pile of toner significantly. However, due to the fluidity of toner and conditions when the crank portion falls by gravity from the top dead center, the crank portion may sink into the pile of toner, causing errors in detecting the amount of toner remaining in the reservoir. Therefore, it was difficult for the conventional toner detector to accurately detect the amount of toner remaining in the toner reservoir.